when I put in the snaps-
1- mark spot on fabric using metal disc. I use a pencil or chalk and mark the 2 lines.
2- cut on marks to make the 2 openings
3- snap prongs go thru right side of fabric
4- plastic (or some use cardboard) circle with slits cut in goes over prongs on wrong side. Metal disc goes over prongs after plastic.
5- Bend prongs toward middle of snap area. Some bend the prongs away from the snap area but I've found the other way better. I usually use the handle of my scissors or rotary cutter to bend the prongs and then push them flat on the table to flatten as much as possible.
6- apply the other half of the snap the same way.
If you have trouble getting the snaps open, I've seen people make a little fabric pocket and putting the snap parts in the pockets and sewing that into the lining. I haven't tried this. Another solution to decrease the pull is to cover the snap with clear nail polish.
Hope this helps
Pat